Fuel injected engines employ fuel injectors, each of which delivers a metered quantity of fuel to an associated engine cylinder during each engine cycle. Prior fuel injectors were of the mechanically or hydraulically actuated type with either mechanical or hydraulic control of fuel delivery. More recently, electronically controlled fuel injectors have been developed. In the case of an electronic unit injector, fuel is supplied to the injector by a transfer pump. The injector includes a plunger which is movable by a cam-driven rocker arm to compress the fuel delivered by the transfer pump to a high pressure. An electrically operated mechanism either carried outside the injector body or disposed within the injector proper is then actuated to cause fuel delivery to the associated engine cylinder.
Prior fuel injector designs have included high pressure fuel passages extending around a central recess containing a solenoid coil and a solenoid armature. Because the overall size of the fuel injector is limited, the size of the solenoid must also be limited, thereby undesirably reducing the available solenoid force. In addition, the high pressure fuel passage must include turns and bends in order not to intersect the solenoid recess, thereby complicating formation of the passages and requiring the use of plugs to seal off portions of the passages after formation. Because of the increase in the path length of the fuel passages, relatively large forces must be placed on the various parts in order to achieve proper sealing, thereby leading to part deflections which can undesirably affect the various components.